1. Field of the Invention
The present invention relates generally to a network data storage system for use with a plurality of host computer nodes, and more specifically, to an adapter (and method of using same) that may be used in such a data storage system to permit data communication among external data exchanging devices and data storage system processors.
2. Brief Description of Related Prior Art
Network computer systems generally include a plurality of geographically separated or distributed computer nodes that are configured to communicate with each other via, and are interconnected by, one or more network communications media. One conventional type of network computer system includes a network storage subsystem that is configured to provide a centralized location in the network at which to store, and from which to retrieve data. Advantageously, by using such a storage subsystem in the network, many of the network's data storage management and control functions may be centralized at the subsystem, instead of being distributed among the network nodes.
One type of conventional network storage subsystem, manufactured and sold by the Assignee of the subject application (hereinafter “Assignee”) under the tradename Symmetrix™, includes a plurality of disk mass storage devices configured as one or more redundant arrays of independent (or inexpensive) disks (RAID). The disk devices are controlled by disk controllers (commonly referred to as “back end” controllers/directors) that are coupled to a shared cache memory resource in the subsystem. The cache memory resource is also coupled to a plurality of host controllers (commonly referred to as “front end” controllers/directors). The disk controllers are coupled to respective disk adapters that, among other things, interface the disk controllers to bus systems (e.g., small computer system interface (SCSI) based bus systems) used to couple the disk devices to the disk controllers. Similarly, the host controllers are coupled to respective host channel adapters that, among other things, interface the host controllers via channel input/output (I/O) ports to the network communications channels (e.g., SCSI, Enterprise Systems Connection (ESCON), or Fibre Channel (FC) based communications channels) that couple the storage subsystem to computer nodes in the computer network external to the subsystem (commonly termed “host” computer nodes or “hosts”).
Each of the disk controllers comprises either one or two respective processors that control, manage, and facilitate transfers of data to and from the disk devices and the shared cache memory in the subsystem. Similarly, each of the host controllers comprises either one or two respective processors (hereinafter termed “host controller processors”) that control, manage, and facilitate transfers of data to and from the shared cache memory in the subsystem and the host nodes.
In the aforesaid conventional storage subsystem manufactured by the Assignee (hereinafter “the Assignee's conventional storage system”), the host adapters include internal data paths that permit communication among the host nodes and the host controller processors. In each respective host adapter, however, these internal data paths do not connect all of the respective I/O ports of that adapter to all of the processors of host controller that is coupled to that adapter. Instead, depending upon the configuration of the Assignee's conventional storage system, the internal data paths of a respective host adapter may only connect two respective I/O ports of that adapter to a single respective host controller processor. Thus, as can be readily appreciated, unless means are provided to enhance the ability of, and flexibility with which, the host controller processors and host nodes may communicate among themselves, an undesirable rigidity may be imposed in the manner in which communications may be effected among host nodes and host controller processors, and the ability of the host nodes and the processors to communicate among themselves may be undesirably limited.
One technique that has been proposed for overcoming these problems and drawbacks of the prior art involves coupling a standalone controllable switch or hub device between the channel I/O ports and the host nodes, so as to permit any channel I/O port to exchange data/commands with any host node. Unfortunately, such devices may be relatively complex and expensive, and substantial amounts of time and effort may be required to properly install such device in the data storage network. Also unfortunately, substantial additional amounts of time and effort may be required to properly configure, manage and maintain such a device after it has been installed in the network.